Japan will make a strong protest to North Korea through diplomatic routes via China, its top cabinet official said on Sunday, after the isolated state fired a ballistic missile into the sea off its east coast.

Speaking to reporters, Chief Cabinet Secretary Yoshihide Suga said North Korea’s missile launch, timed to coincide with a summit between US President Donald Trump and Japanese Prime Minister Shinzo Abe, was a clear act of provocation to Japan and the region.

As Pyongyang’s main diplomatic ally, China is key to any effort to rein in North Korea’s missile programme.